Mount Tongariro in New Zealand (on the North Island) erupted on Monday, August 6th, for the first time in a century. A Suomi-NPP overpass at 12:52 UTC, approximately one hour after the eruption, allowed the day-night band to capture an image of the volcanic plume as it moved eastward across the central part of the North Island. The 3.74 Âµm shortwave IR image and the 11.45 Âµm longwave IR image show that the height of the plume is fairly high: brightness temperatures in the 11.45 Âµm image are around 218 K or -55Âº C. (VIIRS Imagery courtesy of William Straka, UW-Madison/CIMSS). The minor eruption did disrupt air travel, with some flights cancelled in Gisborne, Taupa, Rotorua and Palmerston North.

Volcanic Ash has different emissivity properties at 11 and 12 Âµm; hence, the heritage method for detecting Volcanic Ash uses the difference in brightness temperatures at those two wavelengths. The loop above shows MTSAT-2 imagery; Note the spike in signal in the 1232 UTC image (about 30 minutes after the eruption) that continues to grow as it crosses the coast at 1332 UTC; it then moves rapidly eastward over the ocean.

MTSAT Visible Imagery at 1932 UTC on 6 August 2012

Visible imagery from MTSAT at 1932 UTC, above, approximately 8 hours after the eruption, shows the ash cloud over the ocean east of New Zealand.